CA1044590A - Freeze-thaw method for reducing mineral content of a clay-water mixture - Google Patents
Freeze-thaw method for reducing mineral content of a clay-water mixtureInfo
- Publication number
- CA1044590A CA1044590A CA260,274A CA260274A CA1044590A CA 1044590 A CA1044590 A CA 1044590A CA 260274 A CA260274 A CA 260274A CA 1044590 A CA1044590 A CA 1044590A
- Authority
- CA
- Canada
- Prior art keywords
- water
- mixture
- sludge
- mineral
- clay
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/18—Treatment of sludge; Devices therefor by thermal conditioning
- C02F11/20—Treatment of sludge; Devices therefor by thermal conditioning by freezing
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10C—WORKING-UP PITCH, ASPHALT, BITUMEN, TAR; PYROLIGNEOUS ACID
- C10C3/00—Working-up pitch, asphalt, bitumen
- C10C3/007—Working-up pitch, asphalt, bitumen winning and separation of asphalt from mixtures with aggregates, fillers and other products, e.g. winning from natural asphalt and regeneration of waste asphalt
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/04—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal by extraction
- C10G1/045—Separation of insoluble materials
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S159/00—Concentrating evaporators
- Y10S159/05—Freezing
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Thermal Sciences (AREA)
- Civil Engineering (AREA)
- Materials Engineering (AREA)
- Physics & Mathematics (AREA)
- Structural Engineering (AREA)
- Analytical Chemistry (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Wood Science & Technology (AREA)
- Working-Up Tar And Pitch (AREA)
- Treatment Of Sludge (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method for reducing the clay content of a colloidal clay-water mixture which comprises combining the mixture with air at superatmospheric pressure and thereafter expelling the mixture in the form of small droplets at atmospheric pressure at a temperature below 32°F. to form synthetic snow. Thereafter synthetic snow can be melted to recover water containing reduced mineral content. The invention is particularly applicable to sludge associated with the hot water extraction method for recovering bitumen from tar sands.
A method for reducing the clay content of a colloidal clay-water mixture which comprises combining the mixture with air at superatmospheric pressure and thereafter expelling the mixture in the form of small droplets at atmospheric pressure at a temperature below 32°F. to form synthetic snow. Thereafter synthetic snow can be melted to recover water containing reduced mineral content. The invention is particularly applicable to sludge associated with the hot water extraction method for recovering bitumen from tar sands.
Description
BACKGROUND OF THE INVENTION
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The present lnvention is related to a method for `-~ -separating water rrom a colloldal clay-water mixture. The present invention particularly relates to a method for re-ducing the sludge content of a waste water retention pond ` -a~oclated wlth the hot water method of extracting bitumen from tar sand~, "':
Tar sands, which are also known as oil and bitum_ inous sand~ are siliceous materials which are impregnated ;~
with a heavy petroleum. The largest and most important deposits of the sands are the Athabasca sands, found in northern Alberta, Canada. The~e sands underlay more than 13,000 square mlles at a depth of O to 2,000 reet. Total recoverable reserves after extractlon and processlng Rre e~timated at more than 300 billion barrels. Tar sand~ are primarlly sillca, having clo~ely a~ociated therewlth an oil fllm which varies ~rom about 5 to 21% by welght, wlth a typlcal content Or 13 weight percent of the sand. The oil i8 quite viscous -- 6 to 10 API gravlty -- and con-tains typically 4.5% sulrur and 38% aromatics. In addition to the oil and sand components, tar sands contain clay and silt in quantities of from 1 to 50 ~eight percent, more usually 10 to 30~. The sands also contain a small amount r ~ater, in quantitles of 1 to 10% by weight, in the form o~ a rilm around the sand grain6.
Several baslc extraction methods have been known for many years for the separation of oil from the sand~.
In the so called "cold water" method, the separation is accomplished by mixing the sandg with a solvent capable
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The present lnvention is related to a method for `-~ -separating water rrom a colloldal clay-water mixture. The present invention particularly relates to a method for re-ducing the sludge content of a waste water retention pond ` -a~oclated wlth the hot water method of extracting bitumen from tar sand~, "':
Tar sands, which are also known as oil and bitum_ inous sand~ are siliceous materials which are impregnated ;~
with a heavy petroleum. The largest and most important deposits of the sands are the Athabasca sands, found in northern Alberta, Canada. The~e sands underlay more than 13,000 square mlles at a depth of O to 2,000 reet. Total recoverable reserves after extractlon and processlng Rre e~timated at more than 300 billion barrels. Tar sand~ are primarlly sillca, having clo~ely a~ociated therewlth an oil fllm which varies ~rom about 5 to 21% by welght, wlth a typlcal content Or 13 weight percent of the sand. The oil i8 quite viscous -- 6 to 10 API gravlty -- and con-tains typically 4.5% sulrur and 38% aromatics. In addition to the oil and sand components, tar sands contain clay and silt in quantities of from 1 to 50 ~eight percent, more usually 10 to 30~. The sands also contain a small amount r ~ater, in quantitles of 1 to 10% by weight, in the form o~ a rilm around the sand grain6.
Several baslc extraction methods have been known for many years for the separation of oil from the sand~.
In the so called "cold water" method, the separation is accomplished by mixing the sandg with a solvent capable
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Or di~solving the bitumen constituent. The mixture is then introduced into a large volume of water, water with a sur-face agent added, or a solution of a neutral salt in water, which salt is capable of acting as an electrolyte. The combined mass is then sub~ected to a pressure or gravity separation.
In the hot water method, as di~clo~ed ln Canadian Patent 841,581 lssued May 12, 1970, the bltuminous sands are Jetted wlth steam and mulled with a minor amount of ~-hot water at temperature~ of 170 to 190F, and the re-sulting pulp is then dropped into a turbulent stream of -~
clrculating ho~ water and carrled to a separation cell maintained at a temperature of about 185F. In the ~ep-aration cell, sand settles to the bottom as talling~ and oil rises to the top in the form of a froth. An aqueous middlings layer comprising clay and silt and some oil is formed between these layors. ~his baslc process may be combined wlth a scavenger ~tep for further treatment of the middlings layer obtain~d from the primary separatlon step to recover additional amounts of oil therefrom. The middlings layer, either as it is recovered from the prlmary process or a~ it is recovered after the scavenger step~
comprises water, clay and oil. The oil content is, of cour~e, higher in middlings which have not undergone secondary scavenger steps.
In the hot water extraction process as mentioned above, waste water streams are removcd from the process plant as a slurry of about 35 to 75%, typically 45%, gollds by weight. Included in the slurry is sand, silt, clay and small quantltles of bitumen. In thi~ specifi-cation, sand i8 siliceou~ material which will not pa88 a 325 mesh screen. Silt will pass 325 me~h and is ~maller than 45 microns but i8 larger than two microns.
Clay is material smaller than two microns lncluding some sillceous material of that size, Because this waste water contalns oil emulsions, colloidally dispersed clay wlth poor settling character-istics and other contaminents, water pollution consider-ations prohlbit dlscarding the effluent into rivers, lakes or other natural bodies of water. The disposal of the waste water streams has therefore presented a problem.
Currently, waste water is stored in retontion ponds whlch lnvolve large space requlrements and the construction Or expensive encloaure dikes. A portion of the water in the wast~ water ~troam can be recycled back into tho hot water extractlon process as an economic measure to conserve both heat and water. However, experience has shown that the dispersed silt and clay content of the recycled water can reduce primary froth ., yield by increasing the vlscosity of the middlings layer and retarding the upward settling of oil flecks. When this occuræ, the smaller oil flecks and those that are more heavily laden with mineral matter stay suspended in the water of the separation cell and are removed from the cell with the middlings layer.
Waste water streams discharged from the hot water proce~s for extracting bitumen from tar sand~ contain a ' 590 , ~
~ubstantial amount of mineral matter, much of whlch 1~
colloidally dispersed and does not settle very readily when stored in the retention pond. The lower layer of ~-the retention pond can contain up to 50~ dispersed mineral matter comprised substantially of clay and silt as well as up to 25~ bitumen. This part of the pond ~-water 18 normally referred to as sludge. Sludge is not ~uitable rOr recycling to the hot water extractlon pro-ce~s for the reason that lts additlon lnto tho soparation cell or the scavenger cell at the normal inlet moans would raiso the mineral content of the middlings of the cell to the extent that recovery of bitumen would be substantially reduced. Generally, the settling which does take place in the pond provides a body Or water in which the concen~ration o~ mineral matter increases substantially from the surrace Or tho pond to the bottom thereor.
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As one example, a waste water retention pond as80ciated with a hot water process rOr extracting bitumon rom 140,000 to 150,000 tons Or tar sands per day and having a ~urface area of about l,000 acres and an average depth of 40 feet can be characterized somewhat as follo~s:
(a) From the surface of the pond to a depth of about 15 feet the mineral concentration which is primar11y clay is found to be about 0.5 to 5.0 weight percent. This pond water can normally be recycled to a hot water extrac-tion process without interfering with the extraction of bitumen from tar sandg.
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(b) The layer of water ln the pond between 15 and 25 feet from the surface contains between 5.0 and 20~ ~-mineral matter. Thls water, if recycled to the separation cell feed with fresh tar sands, would increa~e the mineral content of the mlddlings portion of the cell to the point that little bitumen would be recovered.
(c) Flnally the sectlon of the pond botween 25 feet and the bottom of the pond contalns 20 to 5~ mineral mstter and le normally reforred to as sludge, Many procedures for treating waste water associ-ated with the extractlon of bitumen from tar sands have been proposed. For example, Canadian Patent 841,582 issued May 12, 1970 to R. A. Balllie claims a method for; -recovering addltional bltumen from waste water streams recovered from a tar sanda hot water extraction process compri~lng settling the stream and removlng floatlng bitumen rom the ~urface thercof.
U.S. Patent 3,751,358 lasued August 7, 1973 discloses a method for separatlng clarified water from a~ -~
clay-water mlxture whlch comprises agglomerating the clay in the mixture and thereafter freezing then thawing the ~-mixture to separate clarified water therefrom.
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Canadian Patent 824,968 lssued October 14, 1969 to Robert A. Baillie discloses a treatment of waste water from a hot water extraction process which comprises perco-lating the waste water through an inclined sand pile to incorporate the clay and silt of the waste water into the interstices of the sand pile.
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Canadian Patent 866,266 issued ~arch 16, 1971 to Raymond et al. discloses removing bitumen rrom waste uater streams by incorporating vlable microorgani~ms therein whlch subsequently result~ in clay settling.
Canadlan Patent Nos. 873,317 issued June 16, 1971 to Ealllie et al.; 873,318 lssued June 16, 1971 to Baillie et al.; 873,853 issued June 22, 1971 to Baillie et al.;
874,418 is~uod June 29, 1971 to Camp; 874,419 issued June 29, 1971 to Steinmetz; 878,656 lssued Au~ust 17, 1971 to Seitzer et al.; 882,668 issued October 5, 1971 to Camp; 890,804 is~ued January 18, 1972 to Fear et al.;
891,472 lssued January 25, 1972 to Camp; 892,548 lssued February 8, 1972 to Hepp et al. and 917,586 issued December 26, 1972 to Paulson each disclose methods for treating waste water streAms a~sociated with the hok water method for extracting bltumen from tar sands. Yet none Or these proposals provides an economically attractive process for treating hot water oxtraction proces~ wasto uaters a~sociated ~ith the recovery of bitumon from tar sands.
By the method of the present lnventlon an improved process for re~olving this problem i9 provided.
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This invention relates to a method for ~eparatlng water from a colloidal mixture of clay and water. Specifi-cally, the present invention relates to a method for reducing the clay and silt content of waste water streams as~ociated with the aqueous extraction of bitumen from tar sands. More specifically, the present invention comprises a procedure . .
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590 "~ ,., whereby a colloidal dispersion of clay and silt in water is converted into synthetic snow, thereby separating at least a part of the minerals from the water component of the mixture.
Thereafter the snow is melted to provide water decreased in mineral content.
Thus, in accordance with the present teachings, a method is provided for reducing the mineral content of a colloidal mineral-water mixture. The method comprises combining the mixture with air at a pressure of at least 25 psig.
rapidly expanding the air-mineral-water mixture by passing the ~ ~-mixture through a constriction into an atmosphere of sufficiently lower pressure to cause the water in the mixture to atomize and at a temperature below 32F to cause the atomized water to freeze into ice crystals containing the minerals in a concentrated non-colloidal form, and melting the ice crystals containing the concentrated minerals to provide a direct separation of the water and a substantial amount of the concentrated minerals.
The present invention comprises a procedure whereby a mixture of clay and silt dispersed in water such ; as that found in a waste water retention pond associated with -~
the hot water extraction of bitumen from tar sands is transferred at superatmospheric pressure and thereafter expelled as small droplets into the atmosphere at a temperature ~-below 32F. whereby the water fraction of the mixture forms small snow-like crystals thus separating the water from the clay and silt. The water crystals of the stream fall to the ground as synthetic snow, and melt when the temperature rises above 32F. The water obtained from the melted snow no longer contains the colloidal dispersion of minerals. Much of the - clay and silt remain in the area of deposit and the water is free to drain from the area and be recovered.
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:r:: . . ' ' ' ''. ' ' . , s~o Generally the present invention is a freeze-thaw procedure whereby water is separated from colloidal dispersions of clay and silt in water. Specifically, the present method of invention is directed towards solving a problem related ;;~
to the hot water extraction of bitumen from tar sands. As previously noted, one of the undesired products of a hot water extraction procedure for recovering bitumen from tar sands is sludge stored in a retention pond. Reduction of this sludge is very important to this process. The present invention provides one means of accomplishing this end.
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As a general procedure the temperature of the mineral-water mixture to be treated i~ ad~usted to be in the range of 32~F to 40F preferably to a range of about 32F ts 35F. The nearer the temperature of the feed water is to freezing the easier lt i8 to freeze, ~ ;
Thus a feed water ~tream at 32F, can be synthesized into snow at a higher rate than an equivalent stream at a hlghor temperature proceæsed under othorwise identlcal conditions, Lowerlng the tomperaturo o~ the ~e~d stream can be accomplished by passing the mlxture through a heat exchange means of the type generally available for cooling . .
aqueous streams, Theresfter the mlxture is pumped th~ ugh ~ ~-a pressure vessel such as a pipe and preferably admixed with compressed air at a pressure of at least 25 p.s.i,g, and more preferably ln the range of 25 p,s,i,g, to 200 p,æ,i,g, Th~ pressurized mineral-water mixture or air-minoral-water mixture is thereafter passed through a restriction such aæ a nozzle which aids in creating small ~opletæ of the component~ in the stream, When the compre~sed air is used and the air-mineral-water mixture is expelled from the nozzle into an atmo~phere of a substantially lower pressure, the air component of the mixture rapidly expands to effectively cool and atomize at least part of the water in the mixture, Freezing the atomized droplets causes the mineral particles therein to be concentrated as the water fraction freezes so that the frozen particles obtained contain one part com-priæed substantially of frozen water in the form of ice crystals with the remaining part comprised of a mineral concentrate frozen in the ice particle, By this freezing process the colloid dispersion ii8 broken to thereby release mineral free water when the ice crystals melt, _ g _ .... - -, . ~ , " . ~ , - . , -:, i ., S~O
The atmo3phere into which the mlxture i8 expelledis maintained at a temperature below 32F and preferably in the range of +10F to -50F to ~reeze the cooled atomized water from the mixture into small ice crystal~
which give the general appearance of snow. When the ambient temperature rises above 32F the synthetic snow melts and can drain away, thereby completing the separation of the water rrom the mlneral-water mixture.
In a practical sense, sludge from a retention pond is treated by the method of the present inventlon during the ~lnter months of the year when the ambient temperature i~ below freezing at least part Or the time, thereby foregoing the need to artificially freeze the water.
Areas where tar sands exist and extremely cold weather also occurs, such as northern Alberta, Canada, are particularly sultable ~or the practice of the present lnvention.
Normally, the synthotic snow produced by thi~
method 18 deposited over open ground in the ~inter and sub~equently melts and runs off as ground water ln the spring and ~ummer leaving most of the mineral matter deposited on the ground where it was first placed.
Although not c~itical to the invention it is preferable to use sludge containing 40 weight percent or less di~-persed minerals.. Thus a sludge with a higher mineral concentration is more easily processed if it i5 diluted with water prior to treatment. By the proce~s of this invention mineral matter taken from the ground and stored in a retention pond is returned to the ground and thereby removed from water ~hich can be subsequently drained by natural runoff or recovered for reuse in a hot water ex-traction process.
'" . ' ' la.~4~90 Artificial snow 18 made by discharging water or preferably an air and water mlxture under pre sure through a construction into a freezing atmosphere at lower pres~
sure. Snow can be made at any temperature below froezing;
however, ambient air temperatures below 10F are preferred with temperatures in the range of +10F to -50;F bein8 most preferred. It i~ prererred that the mineral-water mlxture ~ ~;
used as feed for making artificial snow 18 supplied at a tomperature ~lightly abovo 32F. Normally, the mineral-water feed mixture should be at a temperature in the range of about 32.5F to 36F but higher temperatures can of course be used.
The mineral-water feed mixture can be supplied at pressures in the range of 25 to 200 p.s.i.g. Air can also be supplied at pressure in the range of 25 to 200 p.s.i.g.
Tho air and tho mlneral-water mlxture can be admlxed at a pressure in the range of 25 to 200 p.s.i.g. and discharged into a ~reezing atmosphere through a nozzle which atomlzes the mixture. On~ type o~ nozzle suitable for u~e ln the proce~s o~ the presont invention i~ disclosed ln Canadian Patent No. 513,432 issued May 31, 1955. Any nozzle design which provldes the necessary dispersion of air and water i3 suitable for use in this process.
A~ one mode o~ the pre~erred proce~s of the pre-sent invention the following example i8 provided.
An aqueous sludge having a temperature of!about 60F is withdrawn from a retention pond which stores wa3te water associated with the hot water extraction of bitumen from tar sands. The sludge is characterized as containing . . . : - . . . . . -.
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1~4~S91;) 4.3~ hydrocarbons, 0.9% sand, 15.8~ ~llt, 7.1% clay and 71.3% water. The sludge is passed through a heat exchang-ing means and recovered at a temperature of about 33F.
The sludge i8 thereafter fed at a rate of 100 USGPM at a pressure of 150 p.s.i.g. to a snow gun approximately 4 feet long and 4 inches in diameter havlng a nozzle on the outlet end 2.5 lnches long and a 1.25 lnch diameter opening. The snow gun contains an inlet means on one end for the addition Or sludg~, Air i8 also added to the ~ludge in the gun at 150 p.8.1.g. and about 700 cubic feet per mlnute. The amblent temperature of the air is at about -6~. Artiflcial snow is formed from the sludge by the rapld expans~on Or the sludge air mixture being ex-pelled from the nozzle of the gun. Upon melting, the artiflclal snow produces water substantlally reduced in mlneral content.
When practlclng the present lnvention lt is pro~erable to remove as much of the hydrocarbon naterial posslble from the sludge if the feed ~ontains more than 1 percent nydrocarbons in the form of tarry bitumen. The bitumen forms agglomerates which on occ~sion can clog small openings in nozzles.
The rate at which sludge can be treated by this procedure i8 dependent upon amblent temperatures and equl ment used. Normally the lower the temperature the higher the feed rate of sludge that 18 possible. Sludge suitable for use in the process of the present invention should contain no more than 40~ solids and pre~erably less than 30~ total solids. Pond water containing less than 5%
minerals is normally suitable for reuse as fresh process water and therefore does not need to be clarified by the proce~ of this lnvention.
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Thus, the present lnvention comprises a method for reducing the mlneral content of a colloldal clay~
w~ er mixture comprising~
Expelling B colloidal clay-water mixture at a pressure of at least 25 p.s.i.g. through a restriction into an atmosphere maintained at a pressure lower than the pressuro of ~aid mlxture and at a temperature below 32F to form l~e crystals from said mixture and there-after moltlng sald ice crystals to rocover ~ater having reduced mlneral content.
Preferably the present invention comprises a method for reducing the mlneral content of a colloidal clay-water mixture comprising:
(a) admlxlng colloidal clay-water mixture containlng at least 5 weight percent dispersed clay with air at a pres~ure of at lea~t 25 p.s.i.g.;
(b) rapidly expanding ~ald air-~ater mixture into an atmosphere of a lower pressure and having a temperature below 32F to cause the water in said mix-ture to atomize and freeze into small ice crystals; and (c) melting aid lce crystals to recover water having reduced mineral content.
More specifically, the present invention provides a method for reducing a sludge content of a ret~ntlon pond containiag ~aste ~aters derived from a hot water extraction process for recovering bitumen from tar sands. Said sludge ~: .
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comprlsing 5 to 50 percent colloidally dispersed mlneral matter in ~ater whlch method comprises:
(a) withdrawing sludge from said pond and ad-mlxing said sludge with alr at a pressure of at least 25 p,s.i.g. and preferably in the range of 25 to 200 p.s.l.g.;
(b) rapidly oxpandlng the air-sludge mlxture ln an atmosphere havlne a lo~or pres~ure and temperature below 32F and preferably belo~ 0F, thereby causing the water in said mixture to atomlzo and form ice crystals;
and -:
(c) meltlng sald ice crystal~ to provide water 3ub~tantlall~ rr - Or collold~lly dlsper~-d mln-ral~.
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Or di~solving the bitumen constituent. The mixture is then introduced into a large volume of water, water with a sur-face agent added, or a solution of a neutral salt in water, which salt is capable of acting as an electrolyte. The combined mass is then sub~ected to a pressure or gravity separation.
In the hot water method, as di~clo~ed ln Canadian Patent 841,581 lssued May 12, 1970, the bltuminous sands are Jetted wlth steam and mulled with a minor amount of ~-hot water at temperature~ of 170 to 190F, and the re-sulting pulp is then dropped into a turbulent stream of -~
clrculating ho~ water and carrled to a separation cell maintained at a temperature of about 185F. In the ~ep-aration cell, sand settles to the bottom as talling~ and oil rises to the top in the form of a froth. An aqueous middlings layer comprising clay and silt and some oil is formed between these layors. ~his baslc process may be combined wlth a scavenger ~tep for further treatment of the middlings layer obtain~d from the primary separatlon step to recover additional amounts of oil therefrom. The middlings layer, either as it is recovered from the prlmary process or a~ it is recovered after the scavenger step~
comprises water, clay and oil. The oil content is, of cour~e, higher in middlings which have not undergone secondary scavenger steps.
In the hot water extraction process as mentioned above, waste water streams are removcd from the process plant as a slurry of about 35 to 75%, typically 45%, gollds by weight. Included in the slurry is sand, silt, clay and small quantltles of bitumen. In thi~ specifi-cation, sand i8 siliceou~ material which will not pa88 a 325 mesh screen. Silt will pass 325 me~h and is ~maller than 45 microns but i8 larger than two microns.
Clay is material smaller than two microns lncluding some sillceous material of that size, Because this waste water contalns oil emulsions, colloidally dispersed clay wlth poor settling character-istics and other contaminents, water pollution consider-ations prohlbit dlscarding the effluent into rivers, lakes or other natural bodies of water. The disposal of the waste water streams has therefore presented a problem.
Currently, waste water is stored in retontion ponds whlch lnvolve large space requlrements and the construction Or expensive encloaure dikes. A portion of the water in the wast~ water ~troam can be recycled back into tho hot water extractlon process as an economic measure to conserve both heat and water. However, experience has shown that the dispersed silt and clay content of the recycled water can reduce primary froth ., yield by increasing the vlscosity of the middlings layer and retarding the upward settling of oil flecks. When this occuræ, the smaller oil flecks and those that are more heavily laden with mineral matter stay suspended in the water of the separation cell and are removed from the cell with the middlings layer.
Waste water streams discharged from the hot water proce~s for extracting bitumen from tar sand~ contain a ' 590 , ~
~ubstantial amount of mineral matter, much of whlch 1~
colloidally dispersed and does not settle very readily when stored in the retention pond. The lower layer of ~-the retention pond can contain up to 50~ dispersed mineral matter comprised substantially of clay and silt as well as up to 25~ bitumen. This part of the pond ~-water 18 normally referred to as sludge. Sludge is not ~uitable rOr recycling to the hot water extractlon pro-ce~s for the reason that lts additlon lnto tho soparation cell or the scavenger cell at the normal inlet moans would raiso the mineral content of the middlings of the cell to the extent that recovery of bitumen would be substantially reduced. Generally, the settling which does take place in the pond provides a body Or water in which the concen~ration o~ mineral matter increases substantially from the surrace Or tho pond to the bottom thereor.
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As one example, a waste water retention pond as80ciated with a hot water process rOr extracting bitumon rom 140,000 to 150,000 tons Or tar sands per day and having a ~urface area of about l,000 acres and an average depth of 40 feet can be characterized somewhat as follo~s:
(a) From the surface of the pond to a depth of about 15 feet the mineral concentration which is primar11y clay is found to be about 0.5 to 5.0 weight percent. This pond water can normally be recycled to a hot water extrac-tion process without interfering with the extraction of bitumen from tar sandg.
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. . . ~. . .- . . . - ..
~ ~ .
- .
(b) The layer of water ln the pond between 15 and 25 feet from the surface contains between 5.0 and 20~ ~-mineral matter. Thls water, if recycled to the separation cell feed with fresh tar sands, would increa~e the mineral content of the mlddlings portion of the cell to the point that little bitumen would be recovered.
(c) Flnally the sectlon of the pond botween 25 feet and the bottom of the pond contalns 20 to 5~ mineral mstter and le normally reforred to as sludge, Many procedures for treating waste water associ-ated with the extractlon of bitumen from tar sands have been proposed. For example, Canadian Patent 841,582 issued May 12, 1970 to R. A. Balllie claims a method for; -recovering addltional bltumen from waste water streams recovered from a tar sanda hot water extraction process compri~lng settling the stream and removlng floatlng bitumen rom the ~urface thercof.
U.S. Patent 3,751,358 lasued August 7, 1973 discloses a method for separatlng clarified water from a~ -~
clay-water mlxture whlch comprises agglomerating the clay in the mixture and thereafter freezing then thawing the ~-mixture to separate clarified water therefrom.
' ' . ~
Canadian Patent 824,968 lssued October 14, 1969 to Robert A. Baillie discloses a treatment of waste water from a hot water extraction process which comprises perco-lating the waste water through an inclined sand pile to incorporate the clay and silt of the waste water into the interstices of the sand pile.
.
~ S9V
Canadian Patent 866,266 issued ~arch 16, 1971 to Raymond et al. discloses removing bitumen rrom waste uater streams by incorporating vlable microorgani~ms therein whlch subsequently result~ in clay settling.
Canadlan Patent Nos. 873,317 issued June 16, 1971 to Ealllie et al.; 873,318 lssued June 16, 1971 to Baillie et al.; 873,853 issued June 22, 1971 to Baillie et al.;
874,418 is~uod June 29, 1971 to Camp; 874,419 issued June 29, 1971 to Steinmetz; 878,656 lssued Au~ust 17, 1971 to Seitzer et al.; 882,668 issued October 5, 1971 to Camp; 890,804 is~ued January 18, 1972 to Fear et al.;
891,472 lssued January 25, 1972 to Camp; 892,548 lssued February 8, 1972 to Hepp et al. and 917,586 issued December 26, 1972 to Paulson each disclose methods for treating waste water streAms a~sociated with the hok water method for extracting bltumen from tar sands. Yet none Or these proposals provides an economically attractive process for treating hot water oxtraction proces~ wasto uaters a~sociated ~ith the recovery of bitumon from tar sands.
By the method of the present lnventlon an improved process for re~olving this problem i9 provided.
.. . .
. '~ .
This invention relates to a method for ~eparatlng water from a colloidal mixture of clay and water. Specifi-cally, the present invention relates to a method for reducing the clay and silt content of waste water streams as~ociated with the aqueous extraction of bitumen from tar sands. More specifically, the present invention comprises a procedure . .
~ 7 -: : .
590 "~ ,., whereby a colloidal dispersion of clay and silt in water is converted into synthetic snow, thereby separating at least a part of the minerals from the water component of the mixture.
Thereafter the snow is melted to provide water decreased in mineral content.
Thus, in accordance with the present teachings, a method is provided for reducing the mineral content of a colloidal mineral-water mixture. The method comprises combining the mixture with air at a pressure of at least 25 psig.
rapidly expanding the air-mineral-water mixture by passing the ~ ~-mixture through a constriction into an atmosphere of sufficiently lower pressure to cause the water in the mixture to atomize and at a temperature below 32F to cause the atomized water to freeze into ice crystals containing the minerals in a concentrated non-colloidal form, and melting the ice crystals containing the concentrated minerals to provide a direct separation of the water and a substantial amount of the concentrated minerals.
The present invention comprises a procedure whereby a mixture of clay and silt dispersed in water such ; as that found in a waste water retention pond associated with -~
the hot water extraction of bitumen from tar sands is transferred at superatmospheric pressure and thereafter expelled as small droplets into the atmosphere at a temperature ~-below 32F. whereby the water fraction of the mixture forms small snow-like crystals thus separating the water from the clay and silt. The water crystals of the stream fall to the ground as synthetic snow, and melt when the temperature rises above 32F. The water obtained from the melted snow no longer contains the colloidal dispersion of minerals. Much of the - clay and silt remain in the area of deposit and the water is free to drain from the area and be recovered.
. . .
': ~
' ~
~-, , - ", . ~ ~ -. .
.. : :, - . . .
:r:: . . ' ' ' ''. ' ' . , s~o Generally the present invention is a freeze-thaw procedure whereby water is separated from colloidal dispersions of clay and silt in water. Specifically, the present method of invention is directed towards solving a problem related ;;~
to the hot water extraction of bitumen from tar sands. As previously noted, one of the undesired products of a hot water extraction procedure for recovering bitumen from tar sands is sludge stored in a retention pond. Reduction of this sludge is very important to this process. The present invention provides one means of accomplishing this end.
. ~:
.', ~'"'.
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.
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-5~(~
As a general procedure the temperature of the mineral-water mixture to be treated i~ ad~usted to be in the range of 32~F to 40F preferably to a range of about 32F ts 35F. The nearer the temperature of the feed water is to freezing the easier lt i8 to freeze, ~ ;
Thus a feed water ~tream at 32F, can be synthesized into snow at a higher rate than an equivalent stream at a hlghor temperature proceæsed under othorwise identlcal conditions, Lowerlng the tomperaturo o~ the ~e~d stream can be accomplished by passing the mlxture through a heat exchange means of the type generally available for cooling . .
aqueous streams, Theresfter the mlxture is pumped th~ ugh ~ ~-a pressure vessel such as a pipe and preferably admixed with compressed air at a pressure of at least 25 p.s.i,g, and more preferably ln the range of 25 p,s,i,g, to 200 p,æ,i,g, Th~ pressurized mineral-water mixture or air-minoral-water mixture is thereafter passed through a restriction such aæ a nozzle which aids in creating small ~opletæ of the component~ in the stream, When the compre~sed air is used and the air-mineral-water mixture is expelled from the nozzle into an atmo~phere of a substantially lower pressure, the air component of the mixture rapidly expands to effectively cool and atomize at least part of the water in the mixture, Freezing the atomized droplets causes the mineral particles therein to be concentrated as the water fraction freezes so that the frozen particles obtained contain one part com-priæed substantially of frozen water in the form of ice crystals with the remaining part comprised of a mineral concentrate frozen in the ice particle, By this freezing process the colloid dispersion ii8 broken to thereby release mineral free water when the ice crystals melt, _ g _ .... - -, . ~ , " . ~ , - . , -:, i ., S~O
The atmo3phere into which the mlxture i8 expelledis maintained at a temperature below 32F and preferably in the range of +10F to -50F to ~reeze the cooled atomized water from the mixture into small ice crystal~
which give the general appearance of snow. When the ambient temperature rises above 32F the synthetic snow melts and can drain away, thereby completing the separation of the water rrom the mlneral-water mixture.
In a practical sense, sludge from a retention pond is treated by the method of the present inventlon during the ~lnter months of the year when the ambient temperature i~ below freezing at least part Or the time, thereby foregoing the need to artificially freeze the water.
Areas where tar sands exist and extremely cold weather also occurs, such as northern Alberta, Canada, are particularly sultable ~or the practice of the present lnvention.
Normally, the synthotic snow produced by thi~
method 18 deposited over open ground in the ~inter and sub~equently melts and runs off as ground water ln the spring and ~ummer leaving most of the mineral matter deposited on the ground where it was first placed.
Although not c~itical to the invention it is preferable to use sludge containing 40 weight percent or less di~-persed minerals.. Thus a sludge with a higher mineral concentration is more easily processed if it i5 diluted with water prior to treatment. By the proce~s of this invention mineral matter taken from the ground and stored in a retention pond is returned to the ground and thereby removed from water ~hich can be subsequently drained by natural runoff or recovered for reuse in a hot water ex-traction process.
'" . ' ' la.~4~90 Artificial snow 18 made by discharging water or preferably an air and water mlxture under pre sure through a construction into a freezing atmosphere at lower pres~
sure. Snow can be made at any temperature below froezing;
however, ambient air temperatures below 10F are preferred with temperatures in the range of +10F to -50;F bein8 most preferred. It i~ prererred that the mineral-water mlxture ~ ~;
used as feed for making artificial snow 18 supplied at a tomperature ~lightly abovo 32F. Normally, the mineral-water feed mixture should be at a temperature in the range of about 32.5F to 36F but higher temperatures can of course be used.
The mineral-water feed mixture can be supplied at pressures in the range of 25 to 200 p.s.i.g. Air can also be supplied at pressure in the range of 25 to 200 p.s.i.g.
Tho air and tho mlneral-water mlxture can be admlxed at a pressure in the range of 25 to 200 p.s.i.g. and discharged into a ~reezing atmosphere through a nozzle which atomlzes the mixture. On~ type o~ nozzle suitable for u~e ln the proce~s o~ the presont invention i~ disclosed ln Canadian Patent No. 513,432 issued May 31, 1955. Any nozzle design which provldes the necessary dispersion of air and water i3 suitable for use in this process.
A~ one mode o~ the pre~erred proce~s of the pre-sent invention the following example i8 provided.
An aqueous sludge having a temperature of!about 60F is withdrawn from a retention pond which stores wa3te water associated with the hot water extraction of bitumen from tar sands. The sludge is characterized as containing . . . : - . . . . . -.
.~ - ~ : . . . , . :
:, .
. . . . -: . . , .. . . . :
1~4~S91;) 4.3~ hydrocarbons, 0.9% sand, 15.8~ ~llt, 7.1% clay and 71.3% water. The sludge is passed through a heat exchang-ing means and recovered at a temperature of about 33F.
The sludge i8 thereafter fed at a rate of 100 USGPM at a pressure of 150 p.s.i.g. to a snow gun approximately 4 feet long and 4 inches in diameter havlng a nozzle on the outlet end 2.5 lnches long and a 1.25 lnch diameter opening. The snow gun contains an inlet means on one end for the addition Or sludg~, Air i8 also added to the ~ludge in the gun at 150 p.8.1.g. and about 700 cubic feet per mlnute. The amblent temperature of the air is at about -6~. Artiflcial snow is formed from the sludge by the rapld expans~on Or the sludge air mixture being ex-pelled from the nozzle of the gun. Upon melting, the artiflclal snow produces water substantlally reduced in mlneral content.
When practlclng the present lnvention lt is pro~erable to remove as much of the hydrocarbon naterial posslble from the sludge if the feed ~ontains more than 1 percent nydrocarbons in the form of tarry bitumen. The bitumen forms agglomerates which on occ~sion can clog small openings in nozzles.
The rate at which sludge can be treated by this procedure i8 dependent upon amblent temperatures and equl ment used. Normally the lower the temperature the higher the feed rate of sludge that 18 possible. Sludge suitable for use in the process of the present invention should contain no more than 40~ solids and pre~erably less than 30~ total solids. Pond water containing less than 5%
minerals is normally suitable for reuse as fresh process water and therefore does not need to be clarified by the proce~ of this lnvention.
.~ . .
- . .
,i ~, ~, . ,~ , . . . .
s9o ~: :
Thus, the present lnvention comprises a method for reducing the mlneral content of a colloldal clay~
w~ er mixture comprising~
Expelling B colloidal clay-water mixture at a pressure of at least 25 p.s.i.g. through a restriction into an atmosphere maintained at a pressure lower than the pressuro of ~aid mlxture and at a temperature below 32F to form l~e crystals from said mixture and there-after moltlng sald ice crystals to rocover ~ater having reduced mlneral content.
Preferably the present invention comprises a method for reducing the mlneral content of a colloidal clay-water mixture comprising:
(a) admlxlng colloidal clay-water mixture containlng at least 5 weight percent dispersed clay with air at a pres~ure of at lea~t 25 p.s.i.g.;
(b) rapidly expanding ~ald air-~ater mixture into an atmosphere of a lower pressure and having a temperature below 32F to cause the water in said mix-ture to atomize and freeze into small ice crystals; and (c) melting aid lce crystals to recover water having reduced mineral content.
More specifically, the present invention provides a method for reducing a sludge content of a ret~ntlon pond containiag ~aste ~aters derived from a hot water extraction process for recovering bitumen from tar sands. Said sludge ~: .
. . . . .
:
, ., . ~ .. .. .. .. . . .
~4~90 ` ~
comprlsing 5 to 50 percent colloidally dispersed mlneral matter in ~ater whlch method comprises:
(a) withdrawing sludge from said pond and ad-mlxing said sludge with alr at a pressure of at least 25 p,s.i.g. and preferably in the range of 25 to 200 p.s.l.g.;
(b) rapidly oxpandlng the air-sludge mlxture ln an atmosphere havlne a lo~or pres~ure and temperature below 32F and preferably belo~ 0F, thereby causing the water in said mixture to atomlzo and form ice crystals;
and -:
(c) meltlng sald ice crystal~ to provide water 3ub~tantlall~ rr - Or collold~lly dlsper~-d mln-ral~.
, , .. ..
' , I .
- 14 _ .... ~ .
. . .
' . :
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for reducing the mineral content of a colloidal mineral-water mixture which comprises:
(a) combining said mixture with air at a pressure of at least 25 p.s.i.g.;
(b) rapidly expanding the air-mineral-water mixture by passing said mixture through a constriction into an atmosphere of sufficiently lower pressure to cause the water in the mixture to atomize and at a temperature below 32°F to cause the atomized water to freeze into ice crystals containing said minerals in a concentrated, non-colloidal form; and (c) melting said ice crystals containing said concentrated minerals to provide a direct separation of the water and a substantial amount of said concentrated minerals.
(a) combining said mixture with air at a pressure of at least 25 p.s.i.g.;
(b) rapidly expanding the air-mineral-water mixture by passing said mixture through a constriction into an atmosphere of sufficiently lower pressure to cause the water in the mixture to atomize and at a temperature below 32°F to cause the atomized water to freeze into ice crystals containing said minerals in a concentrated, non-colloidal form; and (c) melting said ice crystals containing said concentrated minerals to provide a direct separation of the water and a substantial amount of said concentrated minerals.
2. A method according to Claim 1 wherein the pressure of step (a) is in the range of 25 p.s.i.g. to 200 p.s.i.g.
3. A method according to Claim 1 wherein said mineral-water mixture contains between 5.0 and 40.0 weight percent colloidally dispersed mineral matter.
4. A method according to Claim 2 wherein said mineral-water mixture contains between 5.0 and 40.0 weight percent colloidally dispersed mineral matter.
5. A method according to Claim 1 wherein said temperature is in the range of +10°F to -50°F.
6. A method according to Claim 4 wherein said temperature is in the range of +10°F to -50°F.
7. A method for treating aqueous sludge derived from a retention pond used to store waste water derived from a hot water process for recovering bitumen from tar sands, said sludge containing between 5.0 and 40.0 weight percent colloidally dispersed mineral matter to provide water having a lower mineral matter content than the sludge comprising:
(a) providing said sludge from said pond at a temperature in the range of 32°F to 50°F;
(b) combining the sludge with air at a pressure of at least 25 p.s.i.g.;
(c) passing said air-sludge mixture through a constriction into an atmosphere having sufficiently lower pressure to cause the water in the mixture to atomize and having a temperature below 32°F to cause the atom-ized water to form ice crystals containing said minerals in a concentrated, non-colloidal form; and (d) melting said ice crystals containing said concentrated minerals to provide a direct separation of the water and a substantial amount of said concentrated minerals.
(a) providing said sludge from said pond at a temperature in the range of 32°F to 50°F;
(b) combining the sludge with air at a pressure of at least 25 p.s.i.g.;
(c) passing said air-sludge mixture through a constriction into an atmosphere having sufficiently lower pressure to cause the water in the mixture to atomize and having a temperature below 32°F to cause the atom-ized water to form ice crystals containing said minerals in a concentrated, non-colloidal form; and (d) melting said ice crystals containing said concentrated minerals to provide a direct separation of the water and a substantial amount of said concentrated minerals.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/610,953 US4018682A (en) | 1975-09-08 | 1975-09-08 | Freeze-thaw method for reducing mineral content of a clay-water mixture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1044590A true CA1044590A (en) | 1978-12-19 |
Family
ID=24447061
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA260,274A Expired CA1044590A (en) | 1975-09-08 | 1976-08-31 | Freeze-thaw method for reducing mineral content of a clay-water mixture |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4018682A (en) |
| CA (1) | CA1044590A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4250017A (en) * | 1977-03-01 | 1981-02-10 | Reale Lucio V | Process and apparatus for separating tar from a tar sand mixture |
| US4177653A (en) * | 1978-10-20 | 1979-12-11 | Chevron Research Company | Slush filtration method |
| WO1987006573A1 (en) * | 1986-04-30 | 1987-11-05 | Nauchno-Issledovatelsky Institut Kommunalnogo Vodo | Installation for treatment of sediments of natural and sewage waters |
| US6436296B1 (en) | 1995-10-11 | 2002-08-20 | Jeffrey A. White | Waste water treatment method and apparatus |
| CA2160329C (en) * | 1995-10-11 | 2002-02-19 | Jeffrey A. White | Waste water treatment method and apparatus |
| GB0921315D0 (en) | 2009-12-05 | 2010-01-20 | Lemay Patrick | An improved opened geothermal energy system |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2703782A (en) * | 1948-12-11 | 1955-03-08 | London County Council | Treatment of sludges |
| US2780281A (en) * | 1952-01-09 | 1957-02-05 | Herbert H Clark | Treatment of sulphite liquor |
| US3151054A (en) * | 1961-07-06 | 1964-09-29 | Hydrocarbon Research Inc | Treating tar sands |
| US3620776A (en) * | 1968-06-28 | 1971-11-16 | Nestle Sa | Spray drying process |
| US3751358A (en) * | 1972-01-19 | 1973-08-07 | Great Canadian Oil Sands | Freeze-thaw separation of solids from tar sands extraction effluents |
-
1975
- 1975-09-08 US US05/610,953 patent/US4018682A/en not_active Expired - Lifetime
-
1976
- 1976-08-31 CA CA260,274A patent/CA1044590A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4018682A (en) | 1977-04-19 |
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